Wellbores are sometimes drilled into subterranean formations that contain hydrocarbons to allow recovery of the hydrocarbons. The formation materials encountered while drilling into a subterranean formation can vary widely depending on the location and depth of the desired reservoir. In order to properly characterize the materials in a wellbore, one or more samples may be taken and tested to determine a variety of properties of the materials. Specific samples may be taken in various forms including cuttings from the formation in the returned drilling fluids during drilling or special samples cut for testing that are commonly referred to as core samples.
Core samples may be cut using core cutters to produce the samples in a variety of diameters and lengths. The resulting core samples may then be tested in a testing apparatus to determine one or more physical properties of the sample such as the permeability, porosity, fluid flow or fluid or gas saturations in the sample. Special testing apparatuses may be used and specific methods may be carried out to determine the various properties of the samples. Core samples acquired in the subsurface of the earth are generally recovered with a core barrel that either has a disposable inner barrel or a disposable inner barrel liner. At the surface, the core barrel is separated from the coring assembly and placed on the drilling rig floor or other work area.
If the core material is unconsolidated, the core is “stabilized” to prevent mechanical damage caused by handling and shipment. Core stabilization may either be by freezing with dry ice to artificially consolidate the core, or by filling an annular space of the core barrel with a non-reactive core stabilizing compound, for example, epoxy or gypsum. FIG. 1 illustrates, in transverse cross section, an inner barrel or wall 102, enclosing a core sample 104. Because core sample 104 does not completely fill inner barrel or wall 102, a void space 106 remains in an interior of inner barrel 102, which may be filled to prevent core sample 104 from moving within inner barrel or wall 102, to prevent damage to the core by handling and shipment of the samples. In both the epoxy fill or gypsum fill techniques, the inner barrel, which may be thirty feet or more in length, is first sectioned into approximately one meter segments. Each segment is placed on a rack in a near horizontal position to drain any drilling fluid, or mud, from the inner barrel. The base of the segment is then stabilized. After the base is stabilized, the segment is placed in a near vertical position and the entire segment stabilized. Thus, the present methodologies entail substantial handling of the inner barrel and enclosed core sample, and the sample is thus susceptible to mechanical damage caused by vibration, jarring, or other movement.
Thus, there is a need in the art for apparatus and methods that reduce the risk of core damage and the stabilization of core samples in inner barrels. In particular, there is a need in the art for techniques that reduce the movement and handling of the inner barrel, and the contained core in the stabilization process, and, which advantageously permits stabilization of the full length of the inner barrel without the need for segmenting the inner barrel and contained core sample.